It is known in the art to provide a vacuum cleaner having a separating unit, a downstream filter, and a vacuum source for creating a negative air pressure. Such a vacuum cleaner may be configured to operate in a vacuum cleaning mode, in which the vacuum source is connected to the separating unit to force a dust laden airstream therethrough in order to separate dust from the airstream, and the downstream filter is connected between the separating unit and the vacuum source to receive the airstream in a forward direction for filtering remaining dust therefrom. The vacuum cleaner may be switchable to a filter cleaning mode, in which the vacuum source is connected to the downstream filter to force an airstream therethrough in a reverse direction in order to remove dust from the downstream filter, and the separating unit is connected between the downstream filter and the vacuum source to remove dust, released by the downstream filter, from the airstream.
An example of such a vacuum cleaner is disclosed in U.S. Pat. No. 7,951,214, which is incorporated herein by reference. In that document, two downstream filters are used, and when one is clogged by fine dust, the user may switch the places of the filters and clean the clogged filter using the separating unit and the other downstream filter. The cleaned filter is then ready for use when the other filter becomes clogged. Other prior devices use a single downstream filter, but include a series of valves to selectively reconfigure the airflow to pass in reverse through the downstream filter. Devices such as this, and similar devices, are shown in U.S. application Ser. Nos. 12/524,503; 12/676,792 and 12/524,507, which are all incorporated herein by reference.
While the foregoing devices are believed to have practical use, there still remains a need to provide alternative mechanisms and methods for cleaning vacuum cleaner filters.